Doherty amplifiers are amplifiers commonly used in wireless communication systems. Today, for example, Doherty amplifiers are used increasingly in base stations that enable the operation of wireless communications networks. Doherty amplifiers are suitable for use in such applications because the amplifiers include separate amplification paths, typically a carrier path and a peaking path. The two paths are configured to operate at different classes. More particularly, the carrier amplification path typically operates in a class AB mode and the peaking amplification path is biased such that it operates in a class C mode. This enables improved power-added efficiency and linearity of the amplifier, as compared to a balanced amplifier, at the power levels commonly encountered in wireless communications applications.
Generally, a power splitter supplies the input signals to each amplification path in the Doherty amplifier. Power splitters or signal splitters or dividers are known and used, as the name suggests, to divide or split a signal into two or more identical signals. When used in conjunction with a Doherty amplifier, it is important that the attenuation and phase state of each path in the power splitter be properly calibrated for a desired operation of the Doherty amplifier. Because each path can include a very large number of possible attenuation and phase states, it is impractical to inspect the operation of the amplifier at each possible combination of attenuation and phase states in order to identify the optimum calibration.